GB2344867A

GB2344867A - Hydraulic bolt tensioner

Info

Publication number: GB2344867A
Application number: GB9929819A
Authority: GB
Inventors: Nicholas More
Original assignee: Individual
Current assignee: Individual
Priority date: 1998-12-17
Filing date: 1999-12-17
Publication date: 2000-06-21
Anticipated expiration: 2019-12-17
Also published as: GB9929819D0; WO2000035637A1; GB2344867B; GB9827653D0; AU1867200A

Abstract

A hydraulic apparatus 100 for tensioning a bolt includes a piston 110 for engaging a puller sleeve 114 and a cylinder block 106 slidably connected to the piston 110 such that the piston 110 and cylinder block 106 can be forced apart under hydraulic pressure to apply axial force to the puller sleeve 114 to tension a bolt 102. A sleeve 122 is connected to the piston 110 and a series of springs 128 are arranged between the sleeve 122 and cylinder block 106 such that the springs 128 are compressed by movement apart of the piston 110 and cylinder block 106. When the hydraulic pressure is released, the springs 128 urge the piston 110 and cylinder block 106 together to release the axial force applied to the puller sleeve 114.

Description

2344867 H'i"DRAULIC BOLT TENSIONER The present invention relates to

apparatus for hydraulically applying axial tension to bolts.

In forming fastenings including tensioned bolts, for example fastening components together or fastening flanges to pipes, it is established practice to use a hydraulic bolt tensioning tool to extend bolts to which nuts are applied when extended. The tool applies pressure to a component through which a bolt extends and to a reaction member screwed onto the free end of the bolt to urge the component and reaction member apart. This causes axial stress in the bolt, and a nut is tightened on bolt while under tension. When the hydraulic actuating pressure of the bolt tensionina tool is then released, the bolt applies a compression force to the nut and fastening to fon-n a secure fastening.

A partial cross-sectional view of an example of such an arrangement is shown in Figure 1, in which a hydraulic bolt tensioning apparatus 10 applies axial tensiori to a bolt 12 which extends through a component 14 and to which nut 16 is being apphed. The bolt tensioning apparatus 10 applies upward pressure to a threaded reaction member 18 by means of an annular piston 20 having seal 24 and slidably mounted in an annular chamber in cylinder 26. The cylinder 26 is connected to bridging means 28 which extends to the surface of component 14, bridging means 28 including a hexagonal nut tightening means 30.

Hydraulic fluid is introduced under pressure, along the line indicated schematicafly at 32, into the chamber between cylinder 26 and seal 24 to force piston 20 and cylinder 26 apart. As a result, the reaction member, 18 and bridging means 28 are urged apart to apply an axial tension to bolt 12. Once the tension is applied to bolt 12, nut 16 can be tightened using nut tightener 30 and the hydraulic pressure then released to form a secure connection with component 14.

However, the arrangement of Figure I suffers from the drawback that upon release of the hydraulic actuating pressure in apparatus 10, there is no means for causing the hydraulic fluid to return to its reservoir. Therefore in order to return the piston 20 and cylinder 26 to their starting positions, it is necessary to apply sufficient force to the piston 20 to cause the hydraulic fluid to return to its reservoir.

Figures 2 and 3) show partial cross-sectional views of prior art hydraulic bolt tensioning devices which attempt to overcome this problem. In Figure 2, a hydraulic bolt tensioning device 50 comprises a first hydraulic member 52 which is slidably mounted within second hydraulic member 54, both members having respective seal rings 56 and 58. The first and second hydraulic members 52 and 54 can be forced in opposite directions by the introduction, between seals 56 and 58, of a hydraulic fluid under pressure. This will in turn apply a force to threaded reaction member 60 screwed to the free end of a bolt 64 and to bridging means 62 thereby applying an axial tension to bolt 64.

Once sufficient tension has been applied to bolt 64 and nut 66 has been tightened into position, the pressure on the hydraulic fluid can be released. To assist the two hydraulic members 52, 54 in returning to their starting positions (ie that shown in Figure 2), compression springs 68 act between the members 52, 54 to urge the members towards each other and expel hydraulic fluid from between them. In the example shown in Figure 3, the springs 68 have been located below the second hydraulic member 54, with flange 70 attached to an extension to first hydraulic member 52.

The arrangements of Figures 2 and 3 suffer from the disadvantage of requiring two sealing rings and that in practice such devices must be made larger, and therefore at greater cost, than the example shown in Figure 1. Furthermore, in order to construct the apparatus of Figure 2, hydraulic member 54 requires a flange 70 on which springs 68 may operate, and in order that 0 the apparatus may in the first instance be constructed and thereafter be dismantled for maintenance and cleaning, the flange 70 must be removably connected to hydraulic member 54. This is normally done by having holes through flange 70 and threads in hydraulic member 54 into which are screwed bolts (not shown). Such apparatus is therefore time consuming to construct, maintain and repair.

Preferred embodiments of the present invention seek to overcome the above disadvantages of the prior art.

According to the present invention there is provided a hydraulic apparatus for tensioning a bolt, the apparatus comprising- a first member adapted to engage a bolt gripping means; 0 a second member slidably connected to said first member such that said first and second members are adapted to be forced apart under hydraulic pressure to enable said first member to apply axial force to said bolt gripping means to tension a bolt-, a sleeve member connected to said first or second member; and compressible biassing means arranged between said sleeve member and the other of said first or second member, and adapted to be compressed by movement apart of said first and second members, such than when said hydraulic pressure is released, said biassing means urges said first and second members together to release the axial force applied to the bolt gripping means.

By providing an apparatus in which compressible biassing means arranged between the sleeve member and one of the first or second member to urge the first and,'second members together, this provides the advantage that a compact hydraulic bolt tensioning apparatus can be constructed with a self-returning mechanism to move the parts of the apparatus back to their starting positions. The physical dimensions of the apparatus are of particular significance where a series of nut are to be tightened at the same time, for instance around a joint in a pipeline. In this situation a series of bolts are arranged closely around the rim of thejoint. If a small apparatus can be used all of the bolts can be tensioned and nuts tightened at the same time by connecting, in series, an apparatus for each bolt. Suchjoints are often provided with soft metal sealing rings. As a result the bolt may require several tensioning before a complete seal is formed. With an apparatus on each bolt and each apparatus having springs, to return the first and second members to their starting positions, this provides the advantage that apparatus does not need to be moved fforn nut to nut, with the consequence that the time required to perform the operation is significantly reduced, thus offering significant reduction in labour costs.

The advantage is also provided that by providing compressible biassing means arranged between said sleeve member and the other of said first or second member (as opposed to biassing means arranged directly between the first and second members), it is possible to construct the apparatus in such a way that only a sin-le seal is required between the first and 1 C second members, thus reducing the cost of the apparatus and simplifing assembly and maintenance of the apparatus.

In a preferred embodiment said sleeve member is connected to said first or second member by means of a retaining clip in the form of one or more split rings.

The sleeve member is preferably connected to said first or second member by means of a singly said split ring.

By using a single split ring to connect the sleeve to the first or second member the advantage is provided that the apparatus may be easily assembled and disassembled, thus simplifying the initial manufacture and subsequence maintenance and repair processes.

In a preferred embodiment, said first and second members de"e a substantially annular chamber therebetween for receiving hydraulic fluid therein., Preferably, said sleeve member is located in use between said first or second member and said bolt gripping means.

The apparatus advantageously further comprises hydraulic pressure release means for releasing the hydraulic pressure acting between said first and second members when said first and second members are forced apart by a predetermined amount.

By providing pressure release means which is actuated when the first and second members are forced apart by a predetermined amount, this minimises the risk of over-extending the apparatus with the associated danger from escaping hydraulic fluid under high pressure, damage to the apparatus and the potential for parts of the apparatus to dislodge under the hydraulic pressure.

In a preferred embodiment, said pressure release means comprises at least one needle valve arranged between a hydraulic chamber defined between said first or second members into which the other of said first or second members extends and a space adjacent said biassing means, wherein the said valve is adapted to be actuated by said sleeve member coming into contact therewith when said first and second members are forced apart by a predetermined amount.

By providing the hydraulic pressure release means in the form of one or more needle valves which is contained within the apparatus and activated by a part of the sleeve, the advantage is provided that as hydraulic fluid is released the risk of it forming a jet under high pressure externally from the apparatus is minimised, thereby reducing the likelihood of injury resulting from over extension of the apparatus.

The or each said valve may be adapted to discharge hydraulic fluid from said space adjacent said biassing means to the exterior of the apparatus.

This provides the advantage of giving a visible indication that the or each valve has been actuated.

The apparatus may further comprise indicator means for providing an indication that said first and second members are forced apart by a predetermined amount.

The indicator means preferably comprises at least one marking on said first or second member such that the or each said marking inly becomes visible when said first and second members are forced apart by a predetermined amount.

The apparatus may further comprise bolt gripping means for gripping a bolt and adapted to be engaged by said first member.

The bolt gripping means is preferably threaded and adapted to be screwed on to the ftee end of a bolt.

Preferred embodiments of the present invention will now be described, by way of example only, and not in any limitative sense, with reference to the accompanying drawings, in whj&- Figure I is a partial cross-sectional schematic side view of a first example of a prior art hydraulic bolt tensioning device,

Figure 2 is a partial cross-sectional schematic side view of a second example of a prior art hydraulic bolt tensioning device,

Figure 3 is a partial cross-sectional schematic side view of a third example of a prior art hydraulic bolt tensioning device, and

Figure 4 is a partial cross-sectional schematic side view of a hydraulic bolt tensioning apparatus of a first embodiment of the present invention.

Referring to Figure 4, a hydraulic bolt tensioning device 100 is used to apply an axial tensioning force to a bolt 102 which works in cooperation with nut 104 in holding component 106. The device 100 includes a cylinder block 108 into which is cut an arindlar chamber into which fits an annular piston 110. Piston 110 is provided with an annular seal 112 for sealing the annular chamber.

The piston 110 engages a lower surface of an upper part of threaded bolt gripping means in the form of a puller sleeve 114 screwed onto the free end of bolt 102. The lower part of cylinder block 108 rests on a bridge 116 which in turn engages component 106. The bridge 116 has an adaptor 118 for engaging a hexagonal nut 104 such that the nut 104 can be tightened on the bolt 102 by rotating the adaptor I 18 fitted over the nut by means of a tommy bar inserted into holes in the adaptor 118.

A cylindrical sleeve 122 is connected to piston I 10 by a split ring 120 and is located between the cylinder block 108 and puller sleeve 114. The sleeve 122 has a flange 124 which, together with a recess in the cylinder block 108, defines an annular space 126 such that the flange 124 can slide within space 126 relative to cylinder block 108. A series of compression springs 128 act between flange 124 and cylinder block 109 so as to urge the sleeve 122 downwards relative to the cylinder block 108.

A hydraulic fluid inlet 130 is also arranged within cylinder block 108, such that hydraulic fluid can be delivered to the chamber between the cylinder block 108 and piston 110 to drive the cylinder block and piston apart. A needle valve 132 extends between the annular space 126 and the chamber between cylinder block 108 and piston 110, and has a needle 134 projecting into space 126.

The operation of the apparatus 100 of Figure 4 will now be described.

Bolt 102 extends through component 106 against which nut 104 is to be tightened. The bridge 116 is then located over bolt 102 and nut 104 so that it is in contact with component 106. The adaptor 118 is also located over and engages with -nut 104, and the tensioning apparatus 100 is similarly located over bolt 102 such that cylinder block 108 is in contact with bridge 116 and piston 110 comes into contact with puller sleeve 114.

Hydraulic fluid such as oil is then introduced under pressure into the chamber between piston 110 and cylinder block 108 through irilet 130 at inlet point'136. When under pressure this hydraulic fluid causes piston I 10 and cylinder block 108 to slide apart, which in turn, applies a force to bridge 116 and component 106 on the one hand, and puller sleeve 114 and bolt 102 on the other hand. An axial tensioning force is thus applied to bolt 102.

As piston 110 slides within cylinder block 108, sleeve 122 and flange 124 also move relative to cylinder block 108-reducing the size of space 126 and compressing springs 128. As the tensioning force is applied to bolt 102, nut 104 can be tightened by means of adaptor 118, and once nut 104 is tightened, the pressure of the hydraulic fluid can be released. When this occurs, compressed springs 108 expand and cause sleeve 122 and piston 110 to move relative to cylinder block 108, thereby expelling hydraulic fluid through inlet 130.

If further tightening of nut 104 is required, the adaptor 1] 4 is simply rotated further down the thread of bolt 102 and the process of introducing hydraulic fluid under pressure is repeated.

Split ring clip 120 is located in a groove in sleeve 122 and is prevented from sliding along sleeve 122 in either direction. In piston 110 split ring clip 120 is located in a recess thereby preventing the clip 120 and sleeve 122 from sliding relative to piston I 10 in one direction but allow sliding movement in the other direction.

In order that the apparatus 100 may be easily dismantled, flange 124 is provided with at least two holes which can be aligned,-.ith threaded holes in cylinder block 108, therefore extending through space 126. As a result bolts may be inserted through these holes and into the threads and as the bolts are tightened against the force of the springs 128, the sleeve 122 is forced proud ofthepiston 110. Split ring clip 120 once clear of piston 110 can be removed and once clip 120 is removed, piston 110 can be removed from cylinder block 108 and the apparatus dismantled.

If excessive tensioning of the bolt 102 should occur, the flange 124 comes into contact with the needle 134 of needle valve 1-3 32 to cause fluid communication between space 126 and the chamber between the piston 110 and cylinder block 106. This causes hydraulic fluid to be discharged out of the apparatus 100, thus providing a visual indicaion that overtensioning has occurred, as well as releasing hydraulic pressure to niinimise the risk of accident. In addition, the piston 100 is providedwith a visual indicator such as a line at an upper portion thereof which only becomes visible when the piston 110 moves upwards relative to the cylinder block 106 by a predeterniined amount.

It will be appreciated by persons skilled in the art that the above embodiment has been described by way of example only and not in any limitative sense, and that various alterations and modifications are possible without departure from the scope of the invention as defined in the appended claims. Furthen-nore, by the inclusion of the removable sleeve connected to a hydraulic member, the sleeve and both hydraulic members can be constructed from Initially smaller starting components. Therefore the waste material produced as the components are manufactured is reduced, thereby further reducing the manufacturing costs.

Claims

I. A hydraulic apparatus for tensioning a bolt, the apparatus comprisinga first member adapted to engage a bolt gripping meansl a second member slidably connected to said first member such that said first and second members are adapted to be forced apart under hydraulic pressure to enable said first member to apply axial force to said bolt gripping means to tension a bolt, a sleeve member connected to said first or second member; and compressible biassing means arranged between said sleeve member and the other of said first or second member, and adapted to be compressed by movement apart of said first and second members, such than when said hydraulic pressure is released, saiq biassing means urges said first and second members together to release the axial force applied to the bolt gripping means.
2. An apparatus according to claim 1, wherein said sleeve member is connected to said first or second member by means of a retaining chp in the form of one of more split rings.
An apparatus according to claim 2, wherein the sleeve member is connected to said first or second member by means of a single said spht ring.
4. An apparatus according to any one of the preceding claims, wherein said first and second members define a substantially annular chamber therebetween for receiving hydraulic fluid therein.
5. An apparatus according to any one of the preceding claims, wherein said sleeve member is located in use between said first or second member and said bolt gripping means.
6- An apparatus according to any one of the preceding claims, further comprising hydraulic pressure release means for releasing the hNrdraulic pressure acting between said first and second members when said first and second members are forced apart by a predetermined amount.
7. An apparatus according to claim 6, wherein said pressure release means comprises at least one needle valve arranged between a hydraulic chamber defined between said first or second members into which the other of said first or second members extends and a space adjacent said biassing means, wherein the said valve is adapted to be actuated by said sleeve member coming into contact therewith when said first and second members are forced apart by a predetermined amount.
8. An apparatus according to claim 7, wherein the or each said valve is adapted to discharge hydraulic fluid from said space adjacent said biassing means to the exterior of the apparatus.
9. An apparatus according to any one of the preceding claims, further comprising indicator means for providing an indication that said first and second members are forced apart by a predetermined amount.
10. An apparatus according to claim 9, wherein the indicator means comprises at least one marking on said first or second member such that the or each said marking only becomes Visible when said first and second members are forced apart by a predetermined amount.
11. An apparatus according to any one of the preceding claims, further comprising bolt gripping means for gripping a bolt and adapted to be engaged by said first member.
12. A hydraulic apparatus for tensioning a bolt, the apparatus substantially as herembefore described with reference to Figure 4 of the accompanying drawings.